In meeting these percentages, (i) the ordinance shall first emphasize the preservation of existing tree canopy where that canopy meets local standards for health and structural condition, and where it is feasible to do so within the framework of design standards and densities allowed by the local zoning and other development ordinances; and (ii) second, where it is not feasible in whole or in part for any of the justifications listed in subsection E to preserve existing canopy in the required percentages listed above, the ordinance shall provide for the planting of new trees to meet the required percentages.
If, in the opinion of the developer, the project cannot meet the tree preservation target due to the conditions described in subdivision 1, 2, or 3, the developer may request a deviation from the preservation requirement in subsection D. In the request for deviation, the developer shall provide a letter to the locality that provides justification for the deviation, describes how the deviation is the minimum necessary to afford relief, and describes how the requirements of subsection C will be met through tree planting or a tree canopy bank or fund established by the locality. Proposed deviations shall be reviewed by the locality's urban forester, arborist, or equivalent in consultation with the locality's land development or licensed professional civil engineering review staff. The locality may propose an alternative site design based upon adopted land development practices and sound vegetation management practices that take into account the relationship between the cost of conservation and the benefits of the trees to be preserved as described in ANSI A300 (Part 5) 2005 - Management: Tree, Shrub, and Other Woody Plant Maintenance - Standard Practices, Management of Trees and Shrubs During Site Planning, Site Development, and Construction, Annex A, A-1.5, Cost Benefits Analysis (or the latest version of this standard). The developer shall consider the alternative and redesign the plan accordingly, or elect to satisfy the unmet portion of the preservation threshold through on-site tree planting or through the off-site planting mechanisms identified in subsection G, so long as the developer provides the locality with an explanation of why the alternative design recommendations were rejected. Letters of explanation from the developer shall be prepared and certified by a licensed professional engineer as defined in § 54.1-400. If arboricultural issues are part of explanation then the letter shall be signed by a Certified Arborist who has taken and passed the certification examination sponsored by the International Society of Arboriculture and who maintains a valid certification status or by a Registered Consulting Arborist as designated by the American Society of Consulting Arborists. If arboricultural issues are the sole subject of the letter of explanation then certification by a licensed professional engineer shall not be required.
Va. Code § 15.2-961.1